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Research has been undertaken to investigate how the tensile strength efficiency and Z-strength efficiency in twin-wire roll forming is affected when changing formation through the softwood kraft content in a mixture with recycled pulp. The effect of a change in formation through the softwood kraft content and the effect of a change in formation through headbox consistency were also compared. Five kraft contents (0, 25, 50, 75 and 100%) were investigated at volumetric headbox flow rates of 111 and 1,77l/sm. Three additional flow rates were used at a kraft content of 50%. Impaired formation through the softwood kraft content reduced tensile strength efficiency and Z-strength efficiency. Both these properties were similarly affected whether the formation was changed by the softwood kraft content or the headbox consistency. The relative impact of formation was larger for Z-strength efficiency compared with tensile strength efficiency. The reduction in tensile strength efficiency was replicated in a smaller relative increase in tensile strength for machine-made paper than for handsheets made of the furnish. Considering the effect on strength efficiency when evaluating furnishes has been demonstrated as an important concern.

Research has been undertaken to investigate how the tensile strength efficiency and Z-strength efficiency in twin-wire roll forming is affected when changing formation through the softwood kraft content in a mixture with recycled pulp. The effect of a change in formation through the softwood kraft content and the effect of a change in formation through headbox consistency were also compared. Five kraft contents (0, 25, 50, 75 and 100%) were investigated at volumetric headbox flow rates of 111 and 1,77l/sm. Three additional flow rates were used at a kraft content of 50%. Impaired formation through the softwood kraft content reduced tensile strength efficiency and Z-strength efficiency. Both these properties were similarly affected whether the formation was changed by the softwood kraft content or the headbox consistency. The relative impact of formation was larger for Z-strength efficiency compared with tensile strength efficiency. The reduction in tensile strength efficiency was replicated in a smaller relative increase in tensile strength for machine-made paper than for handsheets made of the furnish. Considering the effect on strength efficiency when evaluating furnishes has been demonstrated as an important concern.

Research has been undertaken to investigate how the tensile strength efficiency and Z-strength efficiency in twin-wire roll forming is affected when changing formation through the softwood kraft content in a mixture with recycled pulp. The effect of a change in formation through the softwood kraft content and the effect of a change in formation through headbox consistency were also compared. Five kraft contents (0, 25, 50, 75 and 100%) were investigated at volumetric headbox flow rates of 111 and 1,77l/sm. Three additional flow rates were used at a kraft content of 50%. Impaired formation through the softwood kraft content reduced tensile strength efficiency and Z-strength efficiency. Both these properties were similarly affected whether the formation was changed by the softwood kraft content or the headbox consistency. The relative impact of formation was larger for Z-strength efficiency compared with tensile strength efficiency. The reduction in tensile strength efficiency was replicated in a smaller relative increase in tensile strength for machine-made paper than for handsheets made of the furnish. Considering the effect on strength efficiency when evaluating furnishes has been demonstrated as an important concern.